The present invention pertains generally to the field of medicine and surgery, and more particularly to methods and compositions of matter which may be used to mark the location from which a tissue sample has been removed so that subsequent treatments (e.g., surgical excision, radio-therapy, drug therapy, etc.) may be precisely performed at such location.
A. The Use of Tissue Biopsies in Modern Medicine and Surgery
In modern medical practice small tissue samples, known as biopsy specimens, are often removed from tumors, lesions, organs, muscles and other tissues of the body. Such removal of tissue samples may be accomplished by open surgical technique (i.e., removal of a small sample of tissue through a small surgical incision using a local anesthetic), or through the use of a specialized biopsy instrument such as a biopsy needle. After the tissue samples have been removed, they are typically subjected to diagnostic tests or examinations such as a) gross and microscopic examination to determine cytology and/or histology, b) biochemical analyses to determine the presence or absence of chemical substances which indicate certain disease states, c) microbiological culturing to determine the presence of bacteria or other microbes, and/or d) other diagnostic procedures. The information obtained from these diagnostic tests and/or examinations can then be used to make or confirm diagnoses and/or to formulate treatment plans for the patient.
B. Special Considerations Relating to Biopsy of Breast Cancers
Approximately one in nine American women will develop breast cancer sometime in her life. Breast cancer is presently the most common cancer in women and is the second leading cause of cancer deaths in women. Periodic physical examination of the breasts is important for early detection of potentially cancerous lesions. Additionally, specialized X-ray studies known as mammography is a proven tool for diagnosing breast cancer in women over 40 years of age. Mammography is also believed by many medical practitioners to be diagnostically beneficial in younger women as well. In mammography, the breast is compressed between two plates while specialized x-ray images are taken.
If an abnormal mass in the breast is found by physical examination or mammography, ultrasound may be used to determine whether the mass is a solid tumor or a fluid filled cyst. Cystic lesions are generally benign and the diagnosis of a cystic lesion is often confirmed by needle aspiration of fluid from the interior of the cyst. (It should be noted, however, that the needle aspiration of cystic lesions is different from xe2x80x9cneedle biopsyxe2x80x9d of solid masses as discussed herebelow). However, solid masses are usually subjected to some type of tissue biopsy to determine if the mass is cancerous.
If a solid mass or lesion is large enough to be palpable (i.e., felt by probing with the fingertips) a tissue specimen can be removed from the mass by a variety of techniques, including but not limited to open surgical biopsy or a technique known as Fine Needle Aspiration Biopsy (FNAB). In open surgical biopsy, an incision is made and a quantity of tissue is removed from the mass for subsequent histopathological examination. In the FNAB procedure, a small sample of cells is aspirated from the mass through a needle and the aspirated cells are then subjected to cytological examination.
If a solid mass of the breast is small and non-palpable (e.g., the type typically discovered through mammography), a relatively new biopsy procedure known as xe2x80x9cstereotactic needle biopsyxe2x80x9d may be used. In performing a stereotactic needle biopsy of a breast, the patient lies on a special biopsy table with her breast compressed between the plates of a mammography apparatus and two separate digital x-rays are taken from two slightly different points of view. A computer calculates the exact position of the lesion with X an Y coordinates as well as depth of the lesion within the breast. Thereafter, a mechanical stereotactic apparatus is programed with the coordinates and depth information calculated by the computer, and such apparatus is used to precisely advance the biopsy needle into the small lesion. Depending on the type of biopsy needle (s) used, this stereotactic technique may be used to obtain cytologic specimens (obtained through FNAB) and/or histologic specimens (obtained through coring needle biopsy). Usually at least five separate biopsy specimens are obtained from locations around the small lesion as well as one from the center of the lesion.
i. Potential Time Delay Between Biopsy and Commencement of Surgery or Other Treatment
For some types of biopsies (other than those of breast lesions), xe2x80x9cfrozen sectionsxe2x80x9d of the biopsy specimen may be prepared by a pathologist and such frozen sections may be used to arrive at a reasonably accurate diagnosis within minutes after removal of the biopsy specimen. Such frozen sections are prepared by rapid freezing of the tissue, slicing of the tissue into sections that are approximately greater than 10 microns thick and mounting of the section(s) on glass slides for immediate microscopic examination by a pathologist. Frozen sections of this type are not typically used for biopsies of breast lesions because the usual frozen section is too thick for definitive visualization and diagnosis of the cell types found in breast tumors. Instead, breast biopsy specimens are usually prepared for histopathological examination by a more traditional non-frozen technique wherein the tissue specimen is immersed in a chemical fixative solution (e.g., formalin, glutaraldehyde, etc.) For a period of time sufficient to cause crosslinking of the connective tissue proteins present in the tissue, the fixed tissue is sliced into thin sections approximately 8 microns thick, the tissue sections are mounted on and cell selective histological stains are applied to stain the tissue prior to microscopic examination. This non-frozen tissue preparation technique typically requires at least 24-48 hours to complete and, as a result, the pathologist""s diagnosis of the breast lesion may not be available until 24 to 72 hours after the biopsy specimen was removed from the breast. Thus, for these reasons, histopathological examination and diagnosis of breast lesions may be much more time consuming than the histopathological examination and diagnosis of other types of lesions. Thereafter, if a breast lesion has been diagnosed as cancerous, the patient may require sometime (e.g., several days to more than a week) to consider each of the surgical options available to her, seek second opinion(s) and reach a treatment decision. The available surgical options for cancerous lesions of the breast include various degrees of mastectomy or lumpectomy. Moreover, in some cases, depending on the histology (type of cancer), grade (how aggressive it looks under the microscope), stage (how large the cancer is and how far it has spread), and additional prognostic or predictive information, the treating physicians may recommend that some radiation therapy or chemotherapy be performed before proceeding with surgical lumpectomy.
ii. Marking of Biopsy Sites to Facilitate Subsequent Location and Treatment Of the Lesion
In order for the surgeon or radiation oncologist to direct surgical or radiation treatment to the precise location of the breast lesion several days or weeks after the biopsy procedure was performed, it is desirable that a biopsy site marker be placed in or on the patient""s body to serve as a landmark for subsequent location of the lesion. Various types of biopsy site markers have been known in the prior art. For example, the prior art has included visually discernible markers that are applied externally to the patient""s skin as described in U.S. Pat. Nos. 2,192,270 (Carswell, Jr.) and 5,147,307 (Gluck). Additionally, the prior art has included radiographically visible markers that may be introduced into the biopsy site such as marker wires that are inserted through the biopsy needle after a tissue sample is removed and are thereafter allowed to remain protruding from the patient""s body and radiographically visible tissue markers (e.g., clips or staples) that are attached to tissue adjacent the site from which the biopsy specimen has been removed, as described in International Patent Publication No. WO 98/06346 (Biopsys Medical, inc.). However, due to the consistency of breast tissue and the fact that these biopsy site markers are typically introduced while the breast is still compressed between the mammography plates, these biopsy markers of the prior art may become attached to adjacent bands of connective tissue that do not remain at the specific location of the biopsy after the breast has been decompressed and removed from the mammography apparatus. Furthermore, at least some of the biopsy site markers of the prior art can remain present at the site of implantation for an indefinite period of time if not surgically removed. Thus, if surgery is deemed not to be presently indicated (or if the patient elects not to have surgery performed), the prior art radiographic biopsy site markers can remain intact indefinitely and may obscure or interfere with follow-up or subsequent mammography or imaging studies. Although International Patent Publication No. WO 98/06346 does mention that the clip-type tissue markers disclosed therein may be xe2x80x9cbiodegradablexe2x80x9d such publication provides no information as to what materials could be used to form such a xe2x80x9cbiodegradablexe2x80x9d tissue marker or the preferred time period in which the tissue marker is to remain present (i.e., non-degraded and visible) at the biopsy site.
Thus, there remains a need in the art for the development of biopsy site markers that a) are deliverable into the cavity created by removal of the biopsy specimen (and not into tissue that is located outside of that biopsy cavity), b) will not migrate from the biopsy cavity even when the breast tissue is moved, manipulated or decompressed, c) will remain detectable at the biopsy site (e.g., within the biopsy cavity or at the site where the biopsy cavity once existed) until at least a predetermined first time point (e.g., 2 weeks after the biopsy) to facilitate subsequent location of the biopsy site by a surgeon or radiation oncologist and d) will clear sufficiently from the biopsy site or otherwise not interfere with imaging of the biopsy site and adjacent tissues at a second predetermined time point (e.g., 6 months after the biopsy) so as not to obscure or interfere with follow-up mammography or imaging procedures.
The present invention provides chemical preparations and methods for marking biopsy sites, whereby a detectable marker (i.e., a substance or article that is detectable by imaging and/or palpation and/or visualization) is introduced into the cavity created by removal of a biopsy specimen (e.g., the xe2x80x9cbiopsy cavityxe2x80x9d) such that (i) the marker will remain present and detectable at the biopsy at a first time point (e.g. 2 weeks after introduction), and (ii) the marker will clear sufficiently from the biopsy site, or will otherwise be undetectable by imaging so as not to interfere with follow-up imaging of the biopsy site and adjacent tissues at a second time point (e.g. typically 5-8 months and preferably at about 6 months after introduction).
(i) Imageable Embodiments of the Marker
In embodiments of the invention wherein the marker is detectable by imaging, it will typically be imageable by a suitable imaging means or apparatus. For example, the marker may be radiographically visible (e.g., more radiopaque or more radiolucent than the surrounding tissue so as to be imageable by x-ray, CT scan, mammography, fluoroscopy, or other roentgenological means. In other imageable embodiments, the marker may be imageable by other means such as magnetic resonance imaging (MRI), ultrasound, Doppler, or other presently known or hereafter invented imaging techniques.
(ii) Palpable Embodiments of the Marker
In embodiments of the invention wherein the marker is detectable by palpation, the marker will comprise a space occupying substance or object(s) that, when introduced into the cavity created by the removal of the biopsy specimen, will form a palpable mass that can be located by closed palpation of the breast and/or by local palpation by a surgeon during dissection of the surrounding breast tissue. Space occupying markers that are palpable include balloon(s), beads, microspheres, of flowable bulking materials such as collagen.
(iii) Visually Discernible Embodiments of the Marker
In embodiments of the invention wherein the marker is visually detectable, the marker will comprise a substance or object(s) that is of a color that is different from the color of breast tissue and blood such that, when introduced into the cavity created by the removal of the biopsy specimen, the marker will be visually detectable by a surgeon during dissection of the surrounding breast tissue.
(iv) Energy-Emitting Embodiments of the Marker
In some embodiments of the invention, the marker may emit energy that is detectable by a suitable detection apparatus. For example, the marker may comprise a radioactive substance that is detectable by way of a gamma detector, scintillation counter or other apparatus for detecting radiation. Similarly, the marker may comprise a signal emitting apparatus (e.g. a transmitter or transponder) that will continuously, or occasionally when interrogated by ultrasound or other type of interrogating energy, emit a signal (e.g., radiofrequency, ultrasound, etc.) that can be detected by an apparatus that is useable to detect that particular type of signal.
(v) Embodiments of the Marker That are Detectable by More Than One Detection Means
In some embodiments of the invention, the detectable marker may be detectable by a combination of any two or more of the above-summarized imaging, visual, palpation and/or emission/detection techniques. For example, an imageable marker of the present invention may additionally comprise a palpable component as described above (e.g., a space occupying material or article) so as to render the marker both imageable and palpable after implantation at the biopsy site. Alternatively, an imageable marker of the present invention may additionally be provided with a visible component as described above (e.g., a colored substance or article) so as to render the marker both imageable and visually discernible after implantation at the biopsy site. Similarly, byway of illustrative example, an imageable marker of the present invention may additionally comprise a palpable component as described above (e.g., a space occupying material or article) and a visible component as described above (e.g., a colored substance or article) so as to render the marker imageable, palpable and visible during surgery.
(i) Substantially Insoluble Marker Substances
In accordance with the invention, the detectable marker may comprise a substance (e.g., a gas, lipid, oil, powder, suspension or slurry) that may be delivered into the cavity formed by removal of a biopsy sample (i.e., the xe2x80x9cbiopsy cavityxe2x80x9d), and which has solubility and/or biodistributive properties that allow it to remain present and detectable (e.g., imageable, palpable, energy-emitting and/or visible) at the biopsy site until at least the first predetermined time point (e.g., at least 2 weeks after introduction), but which will allow the substance to be substantially cleared (e.g., dissolved, distributed from or locally metabolized) from the biopsy site at the second predetermined time point (e.g., 6 weeks after introduction).
(ii) Soluble Marker Substances That are Combined with Clearance Delaying Element(s)
Further in accordance with the invention, the detectable marker may comprise a) a detectable (e.g., imageable, palpable, energy-emitting and/or visible) substance that, if delivered alone into the cavity formed by removal of the biopsy specimen, would clear from such biopsy cavity so as to be no longer detectable at the first predetermined time point (e.g., two (2) weeks after introduction) in combination with b) a clearance limiting element (e.g., a diffusion-limiting polymer matrix, a membrane or liposomal encapsulation, a biodegradable matrix or encapsulant, etc. . . . ) that will limit the dissolution, biodistribution and/or local metabolism of the detectable substance to remain present and detectable at the biopsy site for at least 2 weeks after introduction, but which will allow the detectable substance to be substantially cleared (e.g., dissolved, distributed from or locally metabolized) from the biopsy site at the second predetermined time point (e.g., 5-8 months and preferably at about 6 months after introduction).
(iii) Markers That Remain Present at the Biopsy Site Without interfering with Subsequent Follow-Up Imaging Studies
Still further in accordance with the invention, the detectable marker may comprise a substance or article that is detectable by a detection method that is different from the imaging method that is intended to be used for follow-up imaging of the biopsy site and adjacent tissues, thus allowing the marker to reside at the biopsy site beyond the second time point (i.e., that time point at which follow-up imaging studies are to be conducted) or even indefinitely, without interfering with such follow-up imaging studies. For example, the marker may be detectable by palpation, visualization and/or ultrasound but not visible on x-ray, thereby allowing for follow-up x-ray studies without interference by the marker while remaining locatable by palpation, visualization, specialized detection and/or ultrasound in the event that a surgeon, radiologist or other practitioner may wish to subsequently locate the biopsy site.
(iv) Markers That Adhere to the Wall(s) of the Biopsy Cavity
Still further in accordance with the invention, the detectable marker of the present invention may comprise, or may be combined with, an adhesive which will cause the detectable marker to adhere to tissue immediately adjacent the void created by removal of the biopsy sample.
Still further in accordance with the invention, there are provided methods for surgical excision of tissue that is located adjacent to or surrounding a biopsy cavity in which a visually detectable marker of the present invention has been delivered. The method generally comprises the steps of a) visualizing the perimeter of the visually discernible marker and b) excising tissue that lies adjacent to the perimeter of said visually discernible marker. This method of surgical excision may be used to accurately excise and remove a quantity of tissue of a specific width (e.g., a region or band that is 2 centimeters wide) that surrounds or lies adjacent to the original biopsy cavity. Because the biopsy site markers of the present invention actually occupy the original biopsy cavity, they serve to accurately mark the perimeter of that biopsy cavity. As such, the surgeon is able to accurately visualize the boundary of the biopsy cavity and to then excise and remove tissue that lies within a certain distance (e.g., 2 centimeters) of that cavity boundary. Such visualization of the biopsy cavity boundary may be made easier or enhanced when the biopsy site marker comprises, in addition to a visually discernible component such as a dye or carbon particles, a space-occupying bulking agent as described above in reference to palpable embodiments of the invention as the presence of such space occupying or bulking agent may serve to dilate or distend the biopsy cavity, thereby making it easier for the surgeon to visualize the boundaries of that biopsy cavity. This surgical excision method may be particularly suitable in cases where the histopathological evaluation of the biopsy specimen suggests that additional cancerous cells may continue to reside in tissue located within a certain distance of the original biopsy cavity boundary.
Additional objects, embodiments and advantages of the present invention will become apparent to those of skill in the relevant art upon reading and understanding of the following detailed description of preferred embodiments and the accompanying drawings.